This invention relates to a trailer that can experience significantly less drag than a conventional trailer. This invention also relates to a trailer that can be converted from one form to another and more particularly to a trailer that may be easily converted to a much more aerodynamic form, including when empty or partially empty.
As is well known in the art of vehicle design, energy consumption of a vehicle associated with its movement is directly related to certain aerodynamic characteristics of the vehicle, along with inertia, mechanical friction and rolling friction. For example, as the aerodynamic drag (hereinafter referred to as "drag") experienced by a vehicle increases, the fuel costs also correspondingly increase. The experienced drag itself is directly related to an aerodynamic characteristic of the vehicle, sometimes referred to as the drag coefficient Cd of the vehicle. Various components of a vehicle, including any carried structures that are exposed to the elements, can have component drag coefficients Cd themselves, which combine to form an overall vehicle drag coefficient Cd.
Improvements in the aerodynamics of motor vehicles have been made over the last few decades. For passenger vehicles the drag coefficient Cd has been significantly reduced. Attempts have also been made to reduce the drag coefficient Cd of tractor-trailer transport systems 10, an example of which is shown in FIGS. 1A and 1B in side and top view, respectively. Mostly, such modifications have been directed to the tractor or cab 12, and to the open space 14 between the cab 12 and the trailer 16. For example, modifications have been directed to the shape of the cab 12 itself, cowls 17 attached to the cab roof 18, and cowls 19 positioned over the open space 14 between the cab 12 and the trailer 16.
Turbulent flow, represented by the arrows 20 in FIG. 1B, at the rear 22 of the trailer, can be a significant component of tractor-trailer drag. The generation of such flow is contributed to by the shape of a conventional trailer 16, which is essentially a rectangular box having a flat, rectangular roof 24 and matching floor 26, along with flat, rectangular side panels 28. The front and rear surfaces 30 of such trailers are also generally flat rectangular surfaces.
Unfortunately, attempts to make the trailer shape more aerodynamic within the overall length L of the trailer have been accompanied by reduced carrying capacity and interference during loading of the trailer. Also, attempts to make the rear 22 of the trailer more aerodynamic, for example by the addition of panels or inflatable bladders (not shown), can suffer from disadvantages such as added weight and a significant lengthening of the trailer, with associated reductions in fuel efficiency and more difficult handling characteristics.
Therefore, it is desired to have a low cost, strong, lightweight aerodynamic trailer that can have a reduced drag coefficient and therefore reduced fuel costs. In addition, it is desired to have a reduced-drag trailer which does not reduce the potential full load capacity of the tractor-trailer and may be readily converted by one person from a full-load non-aerodynamic form to a partial-load or empty aerodynamic form, thus again facilitating reduced fuel costs.